1. Field of the Invention
The present invention relates to a medium feeding device.
2. Description of the Related Art
Conventionally, there is a known medium feeding device having a configuration in which one medium after another is conveyed as a conveyance target from among a plurality of stacked media. The medium feeding device can sequentially separate the medium of one sheet as a conveyance target from the other media and convey it by introducing the medium into between a feeding roller which conveys the medium in a conveying direction and a brake roller which generates rotational load in a direction counter to the conveying direction.
In such a medium feeding device, it is desirable to avoid a paper feed failure and/or a double feed even when a variety of media which differ in friction characteristics and/or strength are used. For example, Japanese Patent No. 3660547 discloses a technology which appropriately changes the rotational load of the brake roller by controlling an electromagnetic brake. In this way, suitable rotational load can be set for each of a variety of media. This contributes to avoidance of fault, such as a double feed.
Incidentally, there is the demand for improvement in the medium conveying speed of the medium feeding device to increase business efficiency and/or to improve cost performance. In order to secure sufficient performance of separating a medium as a conveyance target from the other media when the medium feeding device operates at a high medium conveying speed, it is necessary for the brake roller to generate the rotational load as promptly as possible when the paper feed failure and/or double feed, etc. occurs.
However, in the conventional technologies disclosed in Japanese Patent No. 3660547, etc., in general an element with large inertia, such as an electromagnetic brake, is used as an element which can change the rotational load. For this reason, when the medium conveying speed is increased, the response at the time of the brake roller generating the rotational load is deteriorated due to the influence of the inertia of a rotational load-changing component. Therefore, in such a case, there is a concern that a medium as a conveyance target may not be reliably separated from the other media.